Mortgage Banking Activities, Net (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Mortgage Loans on Real Estate [Line Items]
Mortgage Banking Activities, Net	$ 53,908	$ 38,691	$ 10,972
Investment Fair Value Changes, Net
Mortgage Loans on Real Estate [Line Items]
Changes in fair value of assets	10,374	(28,574)	(21,357)
Mortgage Banking Activities, Net	53,908	38,691	10,972
Investment Fair Value Changes, Net \| Risk management derivatives, net
Mortgage Loans on Real Estate [Line Items]
Changes in fair value of assets	(12,842)	(9,112)	(9,677)
Residential Mortgage Banking Activities, Net
Mortgage Loans on Real Estate [Line Items]
Other income (expense), net	2,064	2,203	4,040
Mortgage Banking Activities, Net	53,908	40,753	8,268
Residential Mortgage Banking Activities, Net \| Residential loans at fair value
Mortgage Loans on Real Estate [Line Items]
Changes in fair value of assets	69,373	31,399	53,946
Residential Mortgage Banking Activities, Net \| Sequoia securities
Mortgage Loans on Real Estate [Line Items]
Changes in fair value of assets	0	1,455	(15,261)
Residential Mortgage Banking Activities, Net \| Risk management derivatives, net
Mortgage Loans on Real Estate [Line Items]
Changes in fair value of risk management derivatives	(17,529)	5,696	(34,457)
Commercial Mortgage Banking Activities, Net
Mortgage Loans on Real Estate [Line Items]
Mortgage Banking Activities, Net	$ 0	$ (2,062)	$ 2,704

Increase (Decrease) in Fair Value Adjustments on Assets

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- Definition

The net income attributable to mortgage banking activities. This includes market valuations related to residential and commercial loans, Sequoia IOs, and mortgage banking derivatives, as well as realized gains or losses associated with mortgage loan sales.

+ References

No definition available.

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- Definition

Amount of unrealized gain (loss) related to the fair value of price risk derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of fee and financial service revenue classified as other.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(d))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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